Study: ‘Extremely low’ risk of EMS providers getting COVID from patients

Use of PPE and following infection control practices, especially during aerosol-generating procedures, credited for low rate of on-the-job infection


By Greg Friese  

SEATTLE — EMS providers are at extremely low risk of contracting COVID-19 from infected patients, even when treatments involve aerosol-generating procedures, such as intubation, according to a study conducted in Seattle and King County EMS.  

In the study, the researchers examined the work records of 3,000 EMS workers in King County, the metropolitan region encompassing Seattle, during 2020, from mid-February to the end of July.   

“Our findings should help reassure first responders that emergency care in general, and specifically when performing aerosol-generating procedures, can be delivered safely to patients as long as personal protective gear is properly deployed,” Thomas Rea, MD, MPH, King County EMS Medical Director, said.
“Our findings should help reassure first responders that emergency care in general, and specifically when performing aerosol-generating procedures, can be delivered safely to patients as long as personal protective gear is properly deployed,” Thomas Rea, MD, MPH, King County EMS Medical Director, said. (Photo/South King County Fire and Rescue)

An EMS provider was considered potentially exposed to COVID-19 if the patient had a positive SARS-CoV-2 swab sample within 10 days before or three days after the encounter. A provider infection was attributable to such a patient encounter if the provider first tested positive two to 14 days after the encounter. 

During that time, 1,592 of the EMS providers cared for 946 different COVID-19 patients, resulting in a total of 3,710 encounters in which a provider cared for an infected patient. Of those 1,592 EMS providers, 655 (41%) had one encounter with an infected patient, 417 (26%) had two, and 520 (33%) had three or more. In 182 (16%) of these encounters, an aerosol-generating procedure was performed. 

Of the 1,592 potentially-exposed EMS providers, only one tested positive for SARS-CoV-2 within two to 14 days of an encounter with a COVID-19 patient, representing an extremely low incidence of 0.28 cases/10,000 person-days at risk. The single EMS case linked to contact with a COVID-19 patient involved an encounter in which an aerosol-generating procedure was performed.  

“Our findings should help reassure first responders that emergency care in general, and specifically when performing aerosol-generating procedures, can be delivered safely to patients as long as personal protective gear is properly deployed,” Thomas Rea, MD, MPH, King County EMS Medical Director, said. 

An additional 18 EMS providers cared for COVID-19 patients and acquired COVID-19. However, their COVID-19 positive tests were well outside the 14-day incubation period after care. An additional 11 EMS providers who never cared for a patient with COVID-19 also tested positive for COVID-19.  

The research findings appear in the journal Emerging Infectious Diseases, a publication of the U.S. Centers for Disease Control and Prevention. 

Follow PPE protocols on every response 

Researchers noted the importance of adhering to PPE and infection control protocols on every response, as one-third of the COVID-19 patients did not display common symptoms such as fever, cough, or shortness of breath. 

King County EMS personal protection protocols include wearing a mask, eye protection, gloves and a gown. Surgical masks were considered sufficient for treating patients not requiring an aerosol-generating procedure, but an N95 respirator was required when patients underwent such procedures.  

The finding that nearly all COVID-19 cases among EMS workers resulted outside of patient care underscores the importance of social distancing, masking, and handwashing, the researchers said.  

Rea pointed out one notable limitation of the study was that it occurred before the availability of vaccines and the presence of the more contagious delta variant.   

"While provider vaccination might further reduce patient-provider transmission risk, the delta variant could increase risk, as it is more contagious,” Rea said. “The balance of these two new factors is uncertain in this setting and provides impetus to continue to evaluate occupational risk."  

The study was conducted by researchers from the University of Washington School of Medicine and from Public Health – Seattle & King County Division of Emergency Medical Services. Rea, also a professor of general internal medicine at the UW School of Medicine, led the study. The study’s lead author was Aubrey Brown, a senior UW medical student with an interest in high acuity medicine. 

Article adapted from news release written by Michael McCarthy  

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